Polyurethane foam having a phosphonous acid chemically combined therein



United States Patent POLYURETHANE FOAM HAVHNG A PHOS- PHONUUS ACliDCHEMTQALLY (IQMBENED TIPEREIN Blaine 0. Schoepfle, Snyder, and RaymondR. Hindersinn, Lewiston, N.Y., and Michael Worsley, Clyde, Alberta,Canada, assignors to Hooker Chemical (Iorporation, Niagara Falls, N.Y.,a corporation of New York No Drawing. Filed July 17, 1063, fier. No.295,829 9 Claims. (Cl. 260-25) This invention relates to compositionsfor producing fire-resistant foamed or cellular plastic products, and tothe products produced thereby. More particularly, the present inventionresides in compositions for producing fire-resistant polyurethane foamedor cellular plastic products containing chemically combined therein anacidic phosphorus compound. The invention further resides in thecellular products produced therefrom.

The application is a continuation-in-part of copending application,Serial No. 15,516, filed March 17, 1960.

The rigid plastic foams have found Wide and varied use in industry. Forinstance, they may be used as core materials between skins of many andvaried compositions. In aircraft construction the foam may be enclosedbetween aluminum or fiber glass reinforced plastic skins to form anassembly which is rigid, strong and yet remarkably light. Because oftheir excellent electrical properties polyurethane foams have also founduse in the construction of radomes. The polyurethane foams have anotheruseful property, development of a high degree of adhesion during thefoaming process. As a result, they will adhere to skins composed of suchvaried materials as metals, plastics, ceramics, glass, and the like. Theresult ing sandwich-type assemblies lend themselves well to use in suchdiverse fields as the construction and insulation industries. The rigidplastic foams can also be utilized Without skin-s as insulatingmaterials to surround hot water or steam pipes, valves, etc. Theirutility for such applications is enhanced by their ability to beapplied, foamed, and used in situ.

The prior art teaches that polyurethane foams can be rendered more fireresistant by the incorporation of certain plasticizing substances. Amongsuch plasticizing substances are the various neutral phosphate orphosphonate esters or chlorinated compounds. However, such plasticizingsubstances are additives which are not chemically combined with thepolyurethane plastic and are progressively lost from the plastic byevaporation, leaching, and the like. Consequently, such foams do nothave a permanent fire resistance. Furthermore, the plasticizing additiveaffects the physical properties of the foam, particularly with regard tohigh temperature strength.

It is therefore an object of the present invention to provide afoamable, polyurethane composition based on polyesters, polyethers, ormixtures thereof, which foamable compositions can be used for theproduction of cellular plastic materials having a high degree of flameretardance. It is a further object of the present invention to providesuch a composition which has a low viscosity at room temperature so thatit may be handled by conventional equipment. It is a still furtherobject of the present invention to provide such a composition whichattains a high degree of flame retardance while retaining excellentphysical properties so desirable in polyurethane foams, such as goodwater resistance, good high temperature strength, and a minimum amountof foam shrinkage. Further objects and advantages of the presentinvention will appear hereinafter.

In accordance with the present invention, it has been found that fireresistant polyurethane foams having excellent physical properties can beproduced by utilizing a foamable composition which comprises thereaction product of (1) a hydroxyl-containing polymer having a hydroxylnumber of between about twenty-five and nine hundred, (2) an organicpolyisocyanate, and (3) a phosphonous acid.

The present invention can be used to obtain rigid, semirigid or flexiblepolyurethane foams, although the rigid foams are preferred due largelyto the greater need in rigid foams for thermal stability, low viscosityreactants, and fire-resistance.

Various hydroxylcontaining polymers having a hydroxyl number of betweenabout twenty-five and nine hundred can be used in the present invention,for example, a polyester, a polyether or mixtures thereof. The preferredhydroxyl-containing polymers of the present invention are thepolyester-polyether mixtures wherein the polyester portion comprisesfifty percent or more of the polyester-polyether mixture (i.e., when thepolyesterpolyether mixture is at least fifty percent by weightpolyester). Excellent results are obtainable when less than fiftypercent polyester is employed but supplementary additives may bedesirable to render such a foam selfextinguishing. It is especiallypreferred in the present invention to use a mixed polyester-polyether inthe ratio of fifty-five to seventy-five parts polyester to fifteen tothirty-five parts polyether. It has been found that this particularlypreferred range utilizes to best advantage the low cost of thepolyethers, the low viscosity of the polyethers, and the desirableproperties of the polyesters. Generally, the hydroxyl-containingpolymers of the present invention have a molecular Weight of from about200 to about 4,000.

The polyesters are the reaction products of a polyhydric alcohol and apolycarboxylic compound, said polycarboxylic compound being either apolycarboxylic acid, a polycarboxylic acid anhydride, a polycarboxylicacid ester, a polycarboxylic acid halide or mixtures thereof. Among thepolycarboxylic compounds which may be used to form the polyester are:maleic acid; fumaric acid; phthalic acid; tetrachlorophthalic acid; andaliphatic acids such as oxalic, malonic, succinic, glutaric, adipic, andthe like. Additional polycarboxylic compounds which may be used to formthe polyester are Diels-Alder adducts of hexahalocyclopentadiene and apolycarboxylic compound, wherein the halogen is selected from the groupconsisting of chlorine, bromine, fluorine and mixtures thereof, forexample: 1,4,5,6,7,7-hexachlorobicyclo- (2.2.1) 5heptene-2,3-dicarboxylic acid; 1,4,5,6tetrachloro-7,7-difluorobicyclo-(2.2.l) 5 heptene-2,3-dicar boxylicacid; 1,4,5,6,7,7-hexabromobicyclo-(2.2.1) 5- heptene 2,3 dicarboxylicacid; 1,4,5,6-tetrabromo-7,7- difluorobicyclo-(2.2.1)-5-heptene-2,3dicarboxylic acid; etc. Mixtures of any of the above polycarboxyliccompounds may be employed.

To obtain a satisfactory rigid foam, at least a portion of the totalpolyhydric alcohol component should be a polyhydric alcohol containingat least three hydroxyl groups. This provides a means for branching thepolyester. Where an even more rigid structure is desired, the wholealcohol component may be made up of a trifunctional alcohol such asglycerol. Where a less rigid final product is desired, a difunctionalpolyhydric alcohol such as ethylene glycol or 1,4-butanediol may beutilized as that part of the polyhydric alcohol component. Other glycolssuch as diethylene glycol, propylene glycol, and the like, can also beused. Among the polyhydric alcohols which can be used are glycerol,hexanetriol, butanetriol, trimethylol propane, trimethylol ethane,pentaerythritol, and the like. The ratio of the polyhydric alcohol suchas glycerol to the polybasic acid may be expressed as thehydroxyl-carboxyl ratio, which may be defined as the number of moles ofhydroxyl groups to the number of moles of carboxyl groups in a givenweight of resin. This ratio may be varied over a wide range. Generally,however, a hydroxyl-carboxyl ratio of between 1.521 to :1 is employed.

Instead of employing a polycarboxylic compound which is a Diels-Alderadduct of hexahalocyclopentadiene and a polycarboxylic compound, we mayemploy a polyhydric alcohol which is a Diels-Alder adduct ofhexahalocyclopentadiene and a polyhydric alcohol. This can be done byemploying (A) a polyester resin comprised of the reaction product of (1)an adduct of hexahalocyclopentadiene and a polyhydric alcohol containingaliphatic carbon-to-carbon unsaturation, (2) a polycarboxylic compound,and (3) a polyhydric alcohol containing at least three hydroxyl groups.Typical adducts include: 2,3- dimethylol l,4,5,6,7,7hexachlorobicyclo-(2.2.l)-5-heptene; 2,3dimethylol-l,4,5,6-tetrachloro-7,7-difluorobicyclo-(2.2.l)-5-l1eptene,etc. These compounds and others are disclosed in US. Patent No.3,007,958.

Where aromatic or bicyclo carboxylie compounds are used, it is oftendesirable to incorporate aliphatic acids as part of the polyester resin.Suitable acids are adipic, oxalic, malonic, succinic, suberic, azelaic,and the like. Unsaturated acids such as maleic, fumaric, itaconic,citraconic, aconitic, and the like, can also be used.

The preferred polyesters of the present invention are those whichcontain an adduct of hexahalocyclopentadiene co-reacted in the polyesterportion in view of the fact that they contain a large amount of stablechlorine, thereby enhancing the flame-retardant characteristics of theresultant foam. Particularly preferred are those polyesters wherein theadduct is reacted in the polycarboxylic portion of the polyester, due tolower cost, commercial availability and utility of the polycarboxylicadducts of hexahalocyclopentadiene.

The polyethers employed are the reaction products of (l) a polyhydricalcohol, a polycarboxylic acid, and (2) a monomeric 1,2-epoxidepossessing a single 1,2-ep0xy group, such as, for example, propyleneoxide. The polyhydric alcohols and polycarboxylic acids which may beemployed are any of the polyhydric alcohols and polycarboxylic acidshereinbefore listed. Examples of monomeric 1,2-epoxides include ethyleneoxide, propylene oxide, butylene oxide, isobutylene oxide,2,3-epoxyhexane, epichlorohydrin, styrene oxide, glycidyl ether,glycidyl methyl sulfone, glycidyl methacrylate, glycidyl benzoate,glycidyl sorbate, glycidyl allyl phthalate, and the like. The preferredmonoepoxides are the monoepoxide-substituted hydrocarbons, themonoepoxy-substituted ethers, sulfides, sulfones and esters wherein thesaid compounds contain no more than eighteen carbon atoms. A loweralkylene oxide is preferably employed in rigid foams as the highercounterparts yield flexible rather than rigid products.

A large number of various organic diisocyanates can be used. Thearomatic diisocyanates are more reactive and less toxic than thealiphatic members, and are consequently preferred. The compounds whichare at present most readily available commercially are 2,4-tolylenediisocyanate, 2,6-tolylene diisocyanate and mixtures thereof. However,others may be used, among them methylene bis (4-phenylisocyanate),3,3-bitolylene-4,4-diisocyanate, 3, 3-dimethoxy-4,4-biphenylenediisocyanate, naphthalenel,5-diisocyanate, 1,3,5-benzene triisocyanate,polymethylene polyphenylisocyanate, as well as the many impure or crudepolyisocyanates that are commercially available, such as crude mixturesof methylene bis (4-phenylisocyanate).

The diisocyanate concentration can be varied from about seventy-five toone hundred and twenty-five percent of isocyanato groups with respect tothe total number of hydroxyl and carboxyl groups in thehydroxyl-containing polymer and foaming agent (if a foaming agent isemployed). The preferred concentration is about one hundred percent.

Any foaming agent commonly used in the art can be employed. Suitablefoaming agents are those materials capable of liberating gaseousproducts when heated, or when reacted with an isocyanate. The preferredfoaming agents are the fiuorochlorocarbons boiling in the range oftwenty to fifty degrees centigrade, and mixtures thereof, for exampletrichlorofiuoromethane, trichlorotrifluoroethane,dichloromonofiuoromethane, monochloroethane, monochloromonofluoroethane,difiuoromonochloroethane and difiuorodichloroethane.

Anther foaming system which can be used is that comprised of tertiaryalcohols in the presence of strong, concentrated acid catalysts such asis disclosed and claimed in US. Patent No. 2,865,869. Examples oftertiary alcohols include: tertiary amyl alcohol; tertiary butylalcohol; and the like. Examples of catalysts include: sulfuric acid;phosphoric acid; sulfonic acid; and aluminum chloride, etc. In addition,various secondary alcohols can be used such as: l-phenyl-l,Z-ethanediol;Z-butanol; and 2-methyl-2,4-pentanediol; and the like, preferably withstrong, concentrated acid catalysts as above. Other foaming agents thatcan be used include the following: polycarboxylic acids; polycarboxylicacid anhydrides; dimethylol ureas; polymethyl phenols; formic acid andtetrahydroxymethylphosphonium chloride. In addition, mixtures of theabove foaming agents may be employed.

The phosphorus compounds of the present invention are the phosphonousacids. Typical phosphonous acids that can be used have the formula:

wherein R may be alkyl, aryl, or aralkyl, for example, methylphosphonousacid, ethylphosphonous acid, propylphosphonous acid, butylphosphonousacid, phenylphosphonous acid, naphthylphosphonous acid, tolylphosphonousacid, xylylphosphonous acid, and benzylphosphonous acid. The alkyl grouppreferably contains up to six carbon atoms, and the aryl and aralkylgroup preferably contain up to ten carbon atoms to avoid dilution of thephosphorus content. The phosphorus compounds of the present inventionare employed in amounts from about five to thirty percent by weightbased upon the weight of the hydroxyl-containing polymer. The preferredamount is from about eight to about fifteen percent by weight.

The conditions of the procedure for preparing the compositions of thepresent invention may be varied within wide limits. It is preferred toadd the phosphorus compound directly to the hydroxyl-containing polymer,so as to reduce the viscosity, and subsequently add the isocyanatecomponent and foaming agent; however, excellent results are obtainablewhen all the components are simultaneously mixed together, or when thephosphorus compound or compounds is prereacted with the isocyanatecomponent.

Various additives may be incorporated which serve to provide differentproperties. For instance, antimony oxide may be used to improvefire-resistance, fillers, such as clay, calcium sulfate or ammoniumphosphate may be added to lower cost, and improve density andfire-resistance; ingredients such as dyes may be added for color, andfibrous glass, asbestos, or synthetic fibers may be added for strength.

The following examples serve to illustrate the present invention and theimprovements resulting therefrom, but do not limit it. All parts are byweight and temperatures in degrees Centigrade unless specifiedotherwise.

Example 1 (A) A resin was prepared by blending the followingingredients: (1) sixty-five parts by weight of the reaction product oftwo moles of trimethylolpropane and one mole of1,4,5,6,7,7-hexachlorobicyclo-(2.2.1)-5-heptene-2,3-dicarboxylic acidcondensed to an acid number of below ten and having a hydroxyl number of365; (2) twenty-five parts by weight of the reaction product of one moleof trimethylolpropane and six moles of propylene oxide having a hydroxylnumber of 392, and (3) ten parts by weight of benzene phosphonous acid.

(B) To 200 grams of the resin prepared in Example 1 (A) at 50 degreescentigrade was added a solution of (1) sixty grams oftrichlorofluorornethane, and (2) 184 grams of polymethylenepolyphenylisocyanate. The mixture was stirred rapidly for thirtyseconds, and poured into a mold. The resultant foam was cured for tenminutes at 80 degrees centigrade, to provide a foam having a density of1.41 pounds per cubic foot, and a burning rate of 0.34 inch per minuteby the ASTM D-757-49 test.

Example 2 The procedure of Example 1 was repeated except that nophosphorus compound was included in the composition. The resulting foamhad a density of 2.24 pounds per cubic foot, and a burning rate of 11.7inches per minute by the ASTM D-757-49 test.

Example 3 Results comparable to those obtained in Example 1 are obtainedwhen the procedure of Example 1 is repeated except that the phosphoruscompound is methylphosphonous acid, and the polyisocyanate is aprepolymer prepared by reacting 593 grams of1,4,5,6,6,7,7-hexachlorobicycld (2.2.1)-5-heptene-2,3-dicarboxylic acid,and 1,392 grams of a commercial mixture of 80 percent 2,4-tolylenediisocyanate and 20 percent 2,6-tolylene diisocyanate at 80 to 120degrees centigrade.

Example 4 A resin was prepared by blending the following components: (1)85 parts by weight of a polyester derived from 8.8 moles oftrimethylolpropane, five moles of adipic acid and one mole of phthalicanhydride condensed to an acid number of less than one and having ahydroxyl number of 435; and (2) fifteen parts of tris-(B-chloroethyl)phosphate. To 200 grams of this resin at forty-five degrees centrigradewas added a solution of sixty grams of trichlorofluoromethane and twohundred grams of the reaction product prepared in a manner after Example1 (B) from twenty parts of the above polyester and eighty parts of acommercial mixture of eighty percent 2,4- tolylene diisocyanate andtwenty percent 2,6-tolylene diisocyanate. The mixture was stirredrapidly for thirty seconds, then poured into a mold. The foam was curedfor fifteen minutes at 75 degrees centigrade. Attempts to achieve aburning rate of less than 0.5 inch per minute led to swelling of overone hundred percent in humidity ageing and dry heat ageing.

Example 5 Example 4 was repeated, with the exception that tricresylphosphate was utilized instead of tris-(p-chloroethyl) phosphate.Attempts to achieve a burning rate of less than 0.5 inch per minute ledto swelling of over one hundred percent in humidity ageing and dry heatageing.

It should be understood that the present invention also contemplates thepolyphosphorus acids.

When an adduct of hexahalocyclopentadiene is employed, the particlesizes of the hexahalocyclopentadiene adduct should preferably be of tenmesh or smaller, that is have a particle size of 1.68 millimeters orsmaller, in order to avoid gel particles. In the foregoing examples, thehexahalocyclopentadiene adducts employed had a particle size of ten meshor smaller.

This invention can be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects, illustrative, and not restrictive, and all changes which comewithin the meaning and range of equivalency of the claims are intendedto be embraced.

We claim:

1. A polyurethane foam having a phosphonous acid chemically combinedtherein.

2. A fire-resistant cellular reaction product comprising the reactionproduct of 1) a hydroxyl-containing polymer having a hydroxyl number ofbetween about twenty-five and nine hundred, (2) an organic diisocyanate,and (3) a phosphonous acid.

3. A fire-resistant cellular reaction product comprising the reactionproduct of 1) a hydroxyl-containing polymer having a hydroxyl number ofbetween about twenty-five and nine hundred selected from the groupconsisting of a polyester, a polyether and mixtures thereof, (2) anorganic diisocyanate, (3) a phosphonous acid, and (4) a foaming agent.

4. A fire-resistant cellular reaction product according to claim 3wherein the phosphonic acid is benzene phosphonous acid.

5. A fire-resistant cellular reaction product according to claim 3,wherein said hydroxyl-containing polymer is a polyester comprising thereaction product of a polyhydric alcohol and a polycarboxylic compound.

6. A fire-resistant cellular reaction product according to claim 3wherein said hydroxyl-containing polymer is a mixture of a polyester anda polyether containing at least fifty percent by weight of polyester,said polyester comprising the reaction product of a polyhydric alcoholand a polycarboxylic compound, and said polyether comprising thereaction product of a monomeric 1,2-epoxide and a material selected fromthe group consisting of a polyhydric alcohol and a polycarboxylic acid.

7. A fire-resistant cellular reaction product according to claim 6wherein the polycarboxylic acid portion of said polyester contains anadduct of hexahalocyclopentadiene and a polycarboxylic acid, wherein thehalogen is selected from the group consisting of chlorine, bromine,fluorine and mixtures thereof.

8. A fire-resistant cellular reaction product according to claim 7wherein the adduct of hexahalocyclopentadiene is 1,4,5,6,7,7hexachlorobicyclo-(2.2.1)-5-heptene-2,3-dicarboxylic acid.

No references cited.

LEON I. BERCOVITZ, Primary Examiner.

1. A POLYURETHANE FOAM HAVING A PHOSPHONOUS ACID CHEMICALLY COMBINEDTHEREIN.